1. Field of the Invention
The present invention relates to a switched system that accommodates a V5 interface (European Telecommunications Standards ETS300-324, ETS300-347), and in particular, to a multiple method and device for a subscriber access network for a case in which a subscriber of an access network of a particular service provider cannot be directly accommodated in the access network of another service provider that operates the local exchange.
2. Description of the Related Art
FIG. 1 is a conceptual representation of the architecture of a multiple connection for subscriber access network used in the prior art. In this system, which is disclosed in Japanese Patent Laid-open No. 311226/94, when distant terminal 111 is connected to remote terminal 105, the information that connection has occurred is reported to remote terminal 105. Upon receiving the information that connection has occurred, remote terminal 105 makes an entry in a terminal table of distant terminal 111 within remote terminal 105, and based on this information, the cross-connections of circuit channel 110 and subscriber 115 are effected by transmitting on a fixed channel within the circuit channel, thereby realizing a system that allows line concentration of subscriber access network devices connected by multiple connection.
However, the above-described prior art has the following problems:
First, remote terminals in the prior art have both local exchange functions as well as access network functions.
The reason for this is that inclusion of local exchange functions and access network functions means that the V5 protocol functions must also include both local exchange and access network functions, resulting in an extremely large system. In addition, since channel control of the distant terminal is effected by remote terminals, concerns for serviceability dictate control by means of software close to the central office. These factors combine to result in very costly remote terminals.
The second problem is that, in the prior art, the central office and the distant terminal cannot directly exchange messages on a communication channel.
The reason for this is that communication cannot be effected with the distant terminal from the central office by V5 protocol because the communication channel with the distant terminal are terminated at a remote terminal. Processing must therefore be carried out at remote terminals when connecting for every call, and the connection process consequently becomes time consuming.
The third problem is that in the prior art, V5 protocol must be established even between the distant terminal and remote terminals when realizing a V5 interface.
The reason for this is that the subscriber number of a subscriber that is included in the distant terminal is not known at the central office, thereby necessitating a correspondence table for the subscriber number and the employed channel of the line between the distant terminal and remote terminals. This necessity not only makes processing at the central office burdensome and costly, but also prevents the independent establishment and dynamic connection of both channels on the line between a remote terminal and the distant terminal and channels on the line between the central office and remote terminals for every call.
In view of the above-described problems of the prior art, the object of the present invention is to effect control by means of a V5 interface without providing local exchange functions to the access network operated by the service provider of the local exchange when connecting an access network that accommodates subscribers of another network service provider in a multiple connection for a subscriber access network, thereby allowing a reduction in cost, an improvement in serviceability through centralized control, sharing of interfaces by means of V5 interfaces, and dynamic assignment of channels on each line independently for every call.
To realize the above-described objects, the present invention provides a multiple connection method for a subscriber access network that, when connecting an access network that accommodates subscribers of another network service provider to the access network operated by the service provider of the local exchange in a switched system that includes interfaces prescribed by V5 protocol according to standards of the ETSI (European Telecommunications Standards Institute); effects control by V5 interfaces without providing local exchange functions to the access network operated by the service provider of the local exchange.
In addition, as a multiple connection device for a subscriber access network that connects a downstream-link access network accommodating subscribers of another network service provider to an upstream-link access network that is operated by the service provider of the local exchange, the present invention is made up from:
a local exchange that includes: a time switch for concentrating subsidiary lines; LAP (Link Access Procedure) V5 for terminating communication channels prescribed by V5 protocol that connect with access network that are accommodated at lower ranks; another LAP V5 that is disposed for terminating communication channels prescribed by V5 protocol that connect with access networks of another network service providers located at still lower ranks; a dropper/inserter that drops a control channel of V5 protocol to said LAP V5 or inserts a massage from LAP V5 to an appropriate channel; and a CPU that controls V5 protocol, channel assignment on lines, and line concentration;
an upstream-link access network that includes: a time switch that connects channels of lines with said local exchange to channels of lines with lower-ranking access networks; a dropper/inserter that drops or inserts V5 protocol communication messages with a local exchange; LAP V5, which is a V5 protocol terminating device; and a CPU that directs connections of V5 protocol, higher-ranking, and lower-ranking channels; and
a downstream-link access network that includes: a dropper/inserter that drops or inserts V5 protocol communication messages with said local exchange; a time switch that switches connections between line channels and accommodated subscribers; a subscriber circuit having an interface function with accommodated subscribers; LAP V5, which is a V5 protocol terminating device; and a CPU that controls V5 protocol and administers connections of line channels with subscribers.
The present invention allows simplification of a system by not providing upstream-link access networks with the functions of both an access network and a local exchange. In addition, an access network that accommodates subscribers communicates directly with the local exchange by a V5 interface without undergoing intermediation at upstream-link access networks, thereby allowing a reduction in the connection processing time for a call, and in addition, allowing the local exchange to directly recognize the subscriber numbers of a subscriber accommodated in a downstream-link access network. The present invention therefore reduces the call connection time, lowers costs, and eases handling of subscriber numbers.
The above and another objects, features, and advantages of the present invention will become apparent from the following description with reference to the accompanying drawings which illustrate examples of the present invention.